The PDF::Writer library still works very well but the the instructions here (under PDF::Writer (Austin Ziegler) on how the register an “rpdf” template handler don’t apply anymore due to changes in the Rails template system but can easily be fixed:

Aside from normal text substitution it offers support for images and lists. (And all the nice stuff like header/footer or clean page breaks that such word processors offer.)
The API is currently free for low volume usage. I would be very happy to get some feedback.